System and method for variable velocity surgical instrument

ABSTRACT

A system and method of variable velocity control of a surgical instrument in a computer-assisted medical device including an end effector located at a distal end of the instrument, an actuator, and drive mechanisms for coupling force or torque from the actuator to the end effector. To perform an operation with the instrument, the computer-assisted medical device sets a velocity set point of the actuator to an initial velocity, monitors force or torque applied by the actuator, reduces the velocity set point when the applied force or torque is above a first threshold, increases the velocity set point when the applied force or torque is below a second threshold, decreases the velocity set point to zero when the applied force or torque is above a maximum threshold, and drives the actuator based on the velocity set point. The first and second thresholds are lower than the maximum threshold.

RELATED APPLICATIONS

The present disclosure claims priority to U.S. Provisional PatentApplication No. 62/288,784 entitled “System and Method for VariableVelocity Surgical Instrument,” which was filed Jan. 29, 2016, and U.S.Provisional Patent Application No. 62/408,283 entitled “I-Beam StaplerControls Supplement,” which was filed Oct. 14, 2016, both of which arehereby incorporated by reference in their entirety.

TECHNICAL FIELD

The present disclosure relates generally to operation of devices witharticulated arms and end effectors and more particularly to operation ofa minimally invasive surgical instrument with a variable velocitycontrol.

BACKGROUND

More and more devices are being replaced with autonomous andsemiautonomous electronic devices. This is especially true in thehospitals of today with large arrays of autonomous and semiautonomouselectronic devices being found in operating rooms, interventionalsuites, intensive care wards, emergency rooms, and the like. Forexample, traditional manual surgical instruments are being replaced bycomputer-assisted medical devices.

Minimally invasive surgical techniques using computer-assisted medicaldevices generally attempt to perform surgical and/or other procedureswhile minimizing damage to healthy tissue. Some minimally invasiveprocedures may be performed remotely through the use ofcomputer-assisted medical devices with surgical instruments. With manycomputer-assisted medical devices, a surgeon and/or other medicalpersonnel may typically manipulate input devices using one or morecontrols on an operator console. As the surgeon and/or other medicalpersonnel operate the various controls at the operator console, thecommands are relayed from the operator console to a patient side deviceto which one or more end effectors and/or surgical instruments aremounted. In this way, the surgeon and/or other medical personnel areable to perform one or more procedures on a patient using the endeffectors and/or surgical instruments. Depending upon the desiredprocedure and/or the surgical instruments in use, the desired proceduremay be performed partially or wholly under control of the surgeon and/ormedical personnel using teleoperation and/or under semi-autonomouscontrol where the surgical instrument may perform a sequence ofoperations based on one or more activation actions by the surgeon and/orother medical personnel.

Minimally invasive surgical instruments, whether actuated manually,teleoperatively, and/or semi-autonomously may be used in a variety ofoperations and/or procedures and may have various configurations. Manysuch instruments include an end effector mounted at a distal end of ashaft that may be mounted to the distal end of an articulated arm. Inmany operational scenarios, the shaft may be configured to be inserted(e.g., laparoscopically, thorascopically, and/or the like) through anopening (e.g., a body wall incision, a natural orifice, and/or the like)to reach a remote surgical site.

End effectors of different design and/or configuration may be used toperform different tasks, procedures, and functions so as to be allow thesurgeon and/or other medical personnel to perform any of a variety ofsurgical procedures. Examples include, but are not limited to,cauterizing, ablating, suturing, cutting, stapling, fusing, sealing,etc., and/or combinations thereof. Accordingly, end effectors caninclude a variety of components and/or combinations of components toperform these surgical procedures.

Consistent with the goals of a minimally invasive procedure, the size ofthe end effector is typically kept small. One approach to keeping thesize of the end effector small is to accomplish actuation of the endeffector through the use of one or more inputs at a proximal end of thesurgical instrument, where the proximal end is typically locatedexternally to the patient. Various transmission components such asgears, levers, pulleys, cables, rods, belts, bands, and/or the like, maythen be used to transmit actions from the one or more inputs along theshaft of the surgical instrument and to actuate the end effector. In thecase of a computer-assisted, teleoperational medical device with anappropriate surgical instrument, a transmission mechanism at theproximal end of the instrument interfaces directly, or indirectlythrough other transmission components, with one or more actuators suchas various motors, solenoids, servos, active actuators, hydraulics,pneumatics, and/or the like provided on an articulated arm of thepatient side device or a patient side cart. The actuator(s) receivecontrol signals produced in response to user commands provided through amaster controller, and provide input to the instrument involving forceand/or torque at the proximal end of the transmission mechanism; thevarious transmission elements ultimately transmit to actuate the endeffector at the distal end of the transmission mechanism.

Because the size of the end effector is typically small, it may have alimited stiffness that may make is susceptible to flexing and/orsplaying during some grasping, clamping, and/or stapling operations.Operating the instrument at a target velocity that is subject to asimple limit on the amount of applied torque and/or force applied to thetransmission mechanism can often result in a grasping, clamping, and/orstapling operation with failed operations or a ragged velocity profiledue to tissue variations over space or time, and different steps of theoperation such as the different stages of forcing staples through thetissue in a stapling operation.

Accordingly, improved methods and systems for the operation of surgicalinstruments, such as a grasping, clamping, and/or stapling instruments,are desirable. In some examples, it may be desirable to reduce theamount of flexing and/or splaying of the instruments withoutunacceptably slowing down use of the instruments.

SUMMARY

Consistent with some embodiments, a surgical instrument for use with acomputer-assisted medical device includes an end effector located at adistal end of the instrument, an actuator, and one or more drivemechanisms for coupling force or torque from the actuator to the endeffector. To perform an operation with the instrument, thecomputer-assisted medical device is configured to set a velocity setpoint of the actuator to an initial velocity, monitor force or torqueapplied by the actuator, reduce the velocity set point when the appliedforce or torque is above a first threshold, increase the velocity setpoint when the applied force or torque is below a second threshold,decrease the velocity set point to zero when the applied force or torqueis above a maximum threshold, and drive the actuator based on thevelocity set point. The first and second thresholds are lower than themaximum threshold.

Consistent with some embodiments, a surgical instrument for use with acomputer-assisted medical device includes an end effector located at adistal end of the instrument, an actuator, and one or more drivemechanisms for coupling force or torque from the actuator to the endeffector. To perform an operation with the instrument, thecomputer-assisted medical device is configured to operate the endeffector according to a state machine by driving the actuator accordingto a velocity set point. The state machine includes a first clamp state,a second clamp state, and a wait state. In the first clamp state avelocity set point of the actuator is set to a first velocity. In thesecond clamp state the velocity set point of the actuator is set to asecond velocity lower than the first velocity. In the wait state thevelocity set point is set to zero. The state machine transitions fromthe first clamp state to the second clamp state when a force or torqueapplied by the actuator is above a first threshold. The state machinetransitions from the second clamp state to the wait state when the forceor torque applied by the actuator is above a maximum threshold higherthan the first threshold. The state machine transitions from the secondclamp state to the first clamp state when the force or torque applied bythe actuator is below a second threshold.

Consistent with some embodiments, a method of operating a surgicalinstrument for use with a computer-assisted medical device includesperforming operations using one or more processors. The operationsinclude setting a velocity set point of an actuator to an initialvelocity, measuring a force or torque applied by the actuator, reducingthe velocity set point when the applied force or torque is above a firstthreshold, increasing the velocity set point when the applied force ortorque is below a second threshold, decreasing the velocity set point tozero when the applied force or torque is above a maximum threshold, anddriving one or more degrees of freedom of an end effector of thesurgical instrument using the actuator. The first and second thresholdsare lower than the maximum threshold.

Consistent with some embodiments, a non-transitory machine-readablemedium includes a plurality of machine-readable instructions which whenexecuted by one or more processors associated with a computer-assistedmedical device are adapted to cause the one or more processors toperform a method. The method includes setting a velocity set point of anactuator to an initial velocity and measuring a force or torque appliedby the actuator. When the applied force or torque is above a firstthreshold, the method further includes reducing the velocity set point.When the applied force or torque is below a second threshold, the methodfurther includes increasing the velocity set point. When the appliedforce or torque is above a maximum threshold, the method furtherincludes decreasing the velocity set point to zero. And the methodfurther includes driving one or more degrees of freedom of an endeffector of the surgical instrument using the actuator. The first andsecond thresholds are lower than the maximum threshold.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified diagram of a computer-assisted system accordingto some embodiments.

FIG. 2 is a simplified diagram showing a minimally invasive surgicalinstrument according to some embodiments.

FIGS. 3A-3D are simplified diagrams of the end effector of FIG. 2according to some embodiments.

FIG. 4 is a simplified diagram of a state machine for operating an endeffector according to some embodiments.

FIG. 5 is a simplified diagram of a velocity-torque profile an endeffector according to some embodiments.

FIG. 6 is a simplified diagram of a method for performing a stapling andcutting operation according to some embodiments.

In the figures, elements having the same designations have the same orsimilar functions.

DETAILED DESCRIPTION

In the following description, specific details are set forth describingsome embodiments consistent with the present disclosure. It will beapparent to one skilled in the art, however, that some embodiments maybe practiced without some or all of these specific details. The specificembodiments disclosed herein are meant to be illustrative but notlimiting. One skilled in the art may realize other elements that,although not specifically described here, are within the scope and thespirit of this disclosure. In addition, to avoid unnecessary repetition,one or more features shown and described in association with oneembodiment may be incorporated into other embodiments unlessspecifically described otherwise or if the one or more features wouldmake an embodiment non-functional.

Although the following description focuses primarily on embodiments of acombined grasping, stapling, and cutting surgical instrument, one ofordinary skill would understand that the variable velocity methods andmechanisms of the present disclosure may be applied to other medicalinstruments, including surgical and non-surgical instruments. Also,although the following description often discusses a medical device withrobotically articulated arms (also “manipulators) for holding andactuating medical instruments, one of ordinary skill would understandthat the methods and mechanisms of the present disclosure may also beused with computer-assisted medical instruments that are separate fromrobotic arms or articulated arms, including medical instruments designedto be hand-held or attached to non-articulated fixtures.

FIG. 1 is a simplified diagram of a computer-assisted system 100according to some embodiments. As shown in FIG. 1, computer-assistedsystem 100 includes a computer-assisted device 110 with one or moremovable or articulated arms 120. Each of the one or more articulatedarms 120 may support one or more instruments 130. In some examples,computer-assisted device 110 may be consistent with a computer-assistedsurgical device. The one or more articulated arms 120 may each providesupport for medical instruments 130 such as surgical instruments,imaging devices, and/or the like. Examples of medical instruments 130include surgical instruments for interacting with tissue, imaging orsensing devices, and/or the like. In some examples, the instruments 130may include end effectors that are capable of, but are not limited to,performing, gripping, retracting, cauterizing, ablating, suturing,cutting, stapling, fusing, sealing, etc., and/or combinations thereof.

Computer-assisted device 110 may further be coupled to an operatorworkstation (not shown), which may include one or more master controlsfor operating the computer-assisted device 110, the one or morearticulated arms 120, and/or the instruments 130. In some examples, theone or more master controls may include master manipulators, levers,pedals, switches, keys, knobs, triggers, and/or the like. In someembodiments, computer-assisted device 110 and the operator workstationmay correspond to a da Vinci® Surgical System commercialized byIntuitive Surgical, Inc. of Sunnyvale, Calif. In some embodiments,computer-assisted surgical devices with other configurations, fewer ormore articulated arms, and/or the like may be used withcomputer-assisted system 100.

Computer-assisted device 110 is coupled to a control unit 140 via aninterface. The interface may be wired and/or wireless, and may includeone or more cables, fibers, connectors, and/or buses and may furtherinclude one or more networks with one or more network switching and/orrouting devices. Operation of control unit 140 is controlled byprocessor 150. And although control unit 140 is shown with only oneprocessor 150, it is understood that processor 150 may be representativeof one or more central processing units, multi-core processors,microprocessors, microcontrollers, digital signal processors, fieldprogrammable gate arrays (FPGAs), application specific integratedcircuits (ASICs), and/or the like in control unit 140. Control unit 140may be implemented as a stand-alone subsystem and/or board added to acomputing device or as a virtual machine. In some embodiments, controlunit 140 may be included as part of the operator workstation and/oroperated separately from, but in coordination with the operatorworkstation.

Memory 160 may be used to store software executed by control unit 140and/or one or more data structures used during operation of control unit140. Memory 160 may include one or more types of machine readable media.Some common forms of machine readable media may include floppy disk,flexible disk, hard disk, magnetic tape, any other magnetic medium,CD-ROM, any other optical medium, punch cards, paper tape, any otherphysical medium with patterns of holes, RAM, PROM, EPROM, FLASH-EPROM,any other memory chip or cartridge, and/or any other medium from which aprocessor or computer is adapted to read.

As shown in FIG. 1, memory 160 includes a control application 170 thatmay be used to support autonomous, semiautonomous, and/or teleoperatedcontrol of computer-assisted device 110. Control application 170 mayinclude one or more application programming interfaces (APIs) forreceiving position, motion, force, torque, and/or other sensorinformation from computer-assisted device 110, articulated arms 120,and/or instruments 130, exchanging position, motion, force, torque,and/or collision avoidance information with other control unitsregarding other devices, and/or planning and/or assisting in theplanning of motion for computer-assisted device 110, articulated arms120, and/or instruments 130. In some examples, control application 170further supports autonomous, semiautonomous, and/or teleoperated controlof the instruments 130 during a surgical procedure. And although controlapplication 170 is depicted as a software application, controlapplication 170 may optionally be implemented using hardware, software,and/or a combination of hardware and software.

In some embodiments, computer-assisted system 100 may be found in anoperating room and/or an interventional suite. And althoughcomputer-assisted system 100 includes only one computer-assisted device110 with two articulated arms 120 and corresponding instruments 130, oneof ordinary skill would understand that computer-assisted system 100 mayinclude any number of computer-assisted devices with articulated armsand/or instruments of similar and/or different in design fromcomputer-assisted device 110. In some examples, each of thecomputer-assisted devices may include fewer or more articulated armsand/or instruments.

FIG. 2 is a simplified diagram showing a minimally invasive surgicalinstrument 200 according to some embodiments. In some embodiments,surgical instrument 200 may be consistent with any of the instruments130 of FIG. 1. The directions “proximal” and “distal” as depicted inFIG. 2 and as used herein help describe the relative orientation andlocation of components of surgical instrument 200. Distal generallyrefers to elements in a direction further along a kinematic chain from auser or machine holding the instrument 200, a base of acomputer-assisted device for holding the instrument 200, such ascomputer-assisted device 110, and/or or closest to the surgical worksite in the intended operational use of the surgical instrument 200.Proximal generally refers to elements in a direction closer along akinematic chain toward the base of the computer-assisted device, a useror machine holding the instrument 200, and/or one of the articulatedarms of the computer-assisted device for holding the instrument 200.

As shown in FIG. 2, surgical instrument 200 includes a long shaft 210coupling an end effector 220 located at a distal end of shaft 210 towhere the surgical instrument 200 is mounted to an articulated armand/or a computer-assisted device at a proximal end of shaft 210.Depending upon the particular procedure for which the surgicalinstrument 200 is being used, shaft 210 may be inserted through anopening in a patient (e.g., a body wall incision, a natural orifice,and/or the like) in order to place end effector 220 in proximity to aremote surgical site located within the anatomy of a patient. As furthershown in FIG. 2, end effector 220 is generally consistent with a twogripper-style end effector, which in some embodiments may furtherinclude a cutting and/or a stapling mechanism as is described in furtherdetail below with respect to FIGS. 3A-3D. However, one of ordinary skillwould understand that different surgical instruments 200 with differentend effectors 220, such as end effectors with fasteners other thanstaples, are possible and may be consistent with the embodiments ofsurgical instrument 200 as described elsewhere herein.

A surgical instrument, such as surgical instrument 200 with end effector220 typically uses multiple degrees of freedom (DOFs) during itsoperation. Depending upon the configuration of surgical instrument 200and the articulated arm and/or computer-assisted device to which it ismounted, various DOFs that may be used to position, orient, and/oroperate end effector 220 are possible. In some examples, shaft 210 maybe inserted in a distal direction and/or retreated in a proximaldirection to provide an insertion DOF that may be used to control howdeep within the anatomy of the patient that end effector 220 is placed.In some examples, shaft 210 may be able rotate about its longitudinalaxis to provide a roll DOF that may be used to rotate end effector 220.In some examples, additional flexibility in the position and/ororientation of end effector 220 may be provided by one or more jointsand/or links, such as the joints and links of an articulated arm 120,located proximal to shaft 210 and surgical instrument 200. In someexamples, an optional articulated wrist 230 may be used to couple endeffector 220 to the distal end of shaft 210. In some examples,articulated wrist 230 may optionally include one or more rotationaljoints, such as one or more roll, pitch or yaw joints that may provideone or more “roll,” “pitch,” and “yaw” DOF(s), respectively, that may beused to control an orientation of end effector 220 relative to thelongitudinal axis of shaft 210. In some examples, the one or morerotational joints may include a pitch and a yaw joint; a roll, a pitch,and a yaw joint, a roll, a pitch, and a roll joint; and/or the like. Insome examples, end effector 220 further includes a grip DOF used tocontrol the opening and closing of the jaws of end effector 220 and/oran activation DOF used to control the extension, retraction, and/oroperation of a stapling and cutting mechanism as is described in furtherdetail below.

Surgical instrument 200 further includes a drive system 240 located atthe proximal end of shaft 210. Drive system 240 includes one or morecomponents for introducing forces and/or torques to surgical instrument200 that can be used to manipulate the various DOFs supported bysurgical instrument 200. In some examples, drive system 240 mayoptionally include one or more motors, solenoids, servos, activeactuators, hydraulics, pneumatics, and/or the like that are operatedbased on signals received from a control unit, such as control unit 140of FIG. 1. In some examples, the signals may include one or morecurrents, voltages, pulse-width modulated wave forms, and/or the like.In some examples, drive system 240 may optionally include one or moreshafts, gears, pulleys, rods, bands, and/or the like which may becoupled to corresponding motors, solenoids, servos, active actuators,hydraulics, pneumatics, and/or the like that are part of the articulatedarm, such as any of the articulated arms 120, to which surgicalinstrument 200 is mounted. In some examples, the one or more driveinputs, such as shafts, gears, pulleys, rods, bands, and/or the like,are used to receive forces and/or torques from the motors, solenoids,servos, active actuators, hydraulics, pneumatics, and/or the like andapply those forces and/or torques to adjust the various DOFs of surgicalinstrument 200. In this discussion, both “force” and “torque” aresometimes used individually to indicate linear force, rotational torque,and/or both, as applicable.

In some embodiments, the forces and/or torques generated by and/orreceived by drive system 240 are transferred from drive system 240 andalong shaft 210 to the various joints and/or elements of surgicalinstrument 200 located distal to drive system 240 using one or moredrive mechanisms 250. In some examples, the one or more drive mechanisms250 may optionally include one or more gears, levers, pulleys, cables,rods, bands, and/or the like. In some examples, shaft 210 is hollow andthe drive mechanisms 250 pass along the inside of shaft 210 from drivesystem 240 to the corresponding DOFs in end effector 220 and/orarticulated wrist 230. In some examples, each of the drive mechanisms250 may optionally be a cable disposed inside a hollow sheath or lumenin a Bowden cable like configuration. In some examples, the cable and/orthe inside of the lumen may optionally be coated with a low-frictioncoating such as polytetrafluoroethylene (PTFE) and/or the like. In someexamples, as the proximal end of each of the cables is pulled and/orpushed inside drive system 240, such as by wrapping and/or unwrappingthe cable about a capstan or shaft, the distal end of the cable movesaccordingly and applies a suitable force and/or torque to adjust one ormore of the DOFs of end effector 220, articulated wrist 230, and/orsurgical instrument 200.

FIGS. 3A-3D are simplified diagrams of end effector 220 according tosome embodiments. As shown in FIGS. 3A-3D, the distal end of surgicalinstrument 200 or end effector 220 includes a mechanism for jaw closure,tissue stapling, and tissue cutting. And although end effector 220 isshown and described with one fixed and one movable jaw, one of ordinaryskill would understand that the distal end of surgical instrument 200could be modified to use two movable jaws. It should be furtherunderstood that although the description below is in the context of agrasping, stapling, and cutting instrument that simultaneously grasps,staples, and cuts tissue, the aspects so described may be applicable toinstruments with or without cutting features, instruments supportingfusing rather than stapling, and/or the like.

FIG. 3A shows a cut-way side view of end effector 220 prior to actuationso that the jaws of end effector 220 are shown in an open position. Asshown, end effector includes a first jaw 310 that is generally fixed.Jaw 310 is designed to receive a replaceable staple cartridge 320holding a plurality of staples 330 and a plurality of staple pushers335. Staple cartridge 320 is designed to be replaceable so that endeffector 220 is reusable by removing a first staple cartridge 320 afterone or more of the staples 330 are used and replacing it with a secondstaple cartridge 320 having a new set of staples 330 that can be used tofurther perform the surgical procedure. FIG. 3B shows a top view ofstaple cartridge 320. As depicted in FIG. 3B, staple cartridge includesix rows of staple slots 340 through which staples 330 may be applied tograsped tissue upon actuation of end effector 220. The rows of stapleslots 340 include three rows on each side of a cutting slot 350, whichis described in further detail below. Placing staples 330 on both sidesof cutting slot 350 allows for the application of staples 330 to bothsides of a desired cutting line so as to close the tissue on both sidesof the cutting line. The rows of staple slots 340 are also offsetrelative to each other to provide more complete tissue closure alongboth sides of the cutting line. And although, staple cartridge 320 isshown with six rows of offset staple slots 340, each having six stapleslots 340 of uniform size, one of ordinary skill would understand thatfewer or more rows of staple slots with fewer or more staples, stapleslots of varying size, and staple slots of varying patterns arepossible.

As further shown in FIG. 3A, end effector 220 further includes a secondjaw 360 that is movable about a pivot point (not shown) near itsproximal end. In the context of a stapling instrument, second jaw 360may alternatively be referred to as anvil 360. In the embodiments shownin FIG. 3A, anvil 360 includes a transitional edge 370 configured sothat upon initial actuation of end effector 220, a gap between anvil 360and jaw 310 is rapidly reduced until tissue is grasped between anvil 360and jaw 310. Actuation of end effector 220 is accomplished by movementof a reciprocating element 380 from the proximal end of end effector 220to the distal end of end effector 220. Reciprocating element 380 iscoupled to the distal end of one or more of the drive mechanisms 250.

Reciprocating element 380 includes a sled 382 and a flange 384 with acutting blade 386 coupled between the sled 382 and flange 384.Reciprocating element 380 has a general I-beam style cross-sectionalshape as shown in the cut-away end view of end effector 220 shown inFIG. 3D. As end effector 220 is actuated for stapling, sled 382 ispropelled along within jaw 310 and staple cartridge 320 as reciprocatingelement 380 is pushed by drive mechanism 250. Sled 382 includes awedge-shaped leading or distal end such that, as the leading endencounters each of the staple pushers 335, the leading end pushes thestaple pushers 335 against corresponding staples 330. This actionresults in the firing of each of the staples 330 through a respectiveone of the staple slots 340. Although sled 382 is shown with a singlewedge at its leading edge, sled 382 may optionally include separatewedges for each of the rows of staples 330 and staple pushers 335 instaple cartridge 320. Additionally, each of the separate wedges mayoptionally be staggered relative to each other in the direction of sled382 movement. In some embodiments, staple pushers 335 are optional andthe leading edge of sled 382 pushes directly against staples 330. Assled 382 is being propelled along within jaw 310 and staple cartridge320, flange 384 is propelled along within anvil 360. As the leadingdistal end of flange 384 encounters transitional edge 370, flange 384causes initial rapid closure of the gap between anvil 360 and jaw 310.Cutting blade 386 is located somewhat proximally to the distal ends ofsled 382 and flange 384 so that cutting of any grasped tissue trails thefiring of the staples 330 along both sides of the cutting line. Asreciprocating element 380 is actuated, cutting blade 386 travels alongcutting slot 350 as well as a corresponding cutting slot 355 located inanvil 360.

FIGS. 3C and 3D show a cut-away side and a cut-away end view,respectively, of end effector 220 after it has been fully actuated. Asshown, reciprocating element 380, along with sled 382, flange 384, andcutting blade 386, is located at the distal end of end effector 220. Asthe leading edge of sled 382 encounters each of the staple pushers 335,it pushes the staple pushers 335 which in turn push the staples 330 upthrough respective staple slots 340 where they are pressed through anygrasped tissue into a face of anvil 360 where they are bent into finalshape as shown in FIG. 3C. The gap between anvil 360 and jaw 310 ismaintained by the presence of flange 384 within anvil 360. In this way,reciprocating element 380, sled 382, flange 384, and cutting blade 386are all components of end effector 220 which move in response to appliedforce or torque provided by the actuator controlling movement ofreciprocating element 380.

Operation of end effector 220 is subject to several practicalconsiderations as it is actuated. Initially, reciprocating element 380can be moved distally at a high level of velocity with very little forceor torque having to be applied to the drive mechanism 250 used to propelreciprocating element 380. However, as flange 384 begins to encounterleading edge 370 and the gap between anvil 360 and jaw 310 begins torapidly close, any tissue grasped between anvil 360 and jaw 310 beginsto resist further movement of reciprocating element 380. To compensatefor this, drive system 240 applies additional force and/or torque todrive mechanism 250 to maintain the velocity of reciprocating element380. Monitoring of the force and/or torque occurs to make certain that areasonable upper limit is maintained on the applied force and/or torqueto avoid unacceptable flexing and/or splaying of jaw 310 and/or anvil360; damage to end effector 220, drive system 240, and/or drivemechanism 250; and/or damage to the grasped tissue. Second, as thetissue is grasped between anvil 360 and jaw 310, it typically begins todesiccate as fluids are pushed out of the tissue due to the pressure ofthe grasping. As long as the velocity of reciprocating element 380 isappropriately controlled, the amount of force and/or torque to continueadvancing reciprocating element 380 can generally be managed withinreasonable limits for compliant tissue. Third, additional force and/ortorque is typically needed so that sled 382 can push each of the staplepushers 335 against the staples 330 so that the staples 330 are pushedthrough the grasped tissue and/or cutting blade 386 can cut the graspedtissue, while maintaining a desired velocity for reciprocating element380. This additional force and/or torque may vary significantly asproperties of the tissue being stapled change, previously applied staplelines are crossed, and/or the like.

To achieve a smooth operation of end effector 220, it is generallydesired to actuate reciprocating element 380 with a constant velocitythroughout initial contact with the tissue, firing of staples 330, andcutting of the grasped and stapled tissue. In some embodiments, thisoccurs with monitoring and/or limiting the applied force and/or torqueso as to reduce and/or avoid unacceptable flexing and/or splaying of jaw310 and/or anvil 305; damage to end effector 220, drive system 240,and/or drive mechanism 250; and/or damage to the grasped tissue. Oneapproach is to operate end effector 220 using a constant velocity setpoint subject to a maximum force and/or torque limit on drive system240. The constant velocity set point can be selected to provide abalance between speed of operation and risk of encountering the forceand/or torque limit. In some examples, the constant velocity set pointmay optionally be adjustable, such as by an operator, based on a type oftissue that is being grasped, stapled, and clamped. In some embodimentsand/or under certain operating conditions, particular velocity setpoints and/or ranges of velocity set points may result in less thanoptimal operation of end effector 220 either due to a too low constantvelocity set point, ragged operation due to constant encounters with theforce and/or torque limit that cause the reciprocating element 380 toslow down and speed up in a possibly erratic pattern, and/or the like.

Improved performance of end effector 220 and a smoother operation arepossible using a velocity profile for reciprocating element 380 thatadapts based on the force and/or torque being applied by drive system240 and drive mechanism 250. For example, as forces and/or torques beginto increase, the velocity of reciprocating element 380 is decreased in acontrolled fashion, and as forces and/or torques begin to decrease, thevelocity of reciprocating element 380 is increased in a controlledfashion. In this way smoother operation of end effector 220 is obtainedcompared to relying on a single force and/or torque limit to indirectlyslow down the velocity of reciprocating element 380. For example,slowing down when a force and/or torque threshold lower than a maximumforce and/or torque limit may result in operation with fewer starts andstops as the reciprocating element 380 bogs down at the maximum forceand/or torque limit.

According to some embodiments, other techniques may be used foradjusting velocity. For example, as forces and/or torques pass athreshold amount, the velocity of reciprocating element 380 may be setto a current detected velocity of reciprocating element 380 and/or avelocity set point slightly lower than the current detected velocity.

Referring back to FIG. 3A, also shown in is an arrow 390 indicating thedirection of travel of reciprocating element 380 during actuation of anexample stapling process. A set of dotted lines 392, 394, 396, 398indicate particular locations that the distal tip of sled 382 reachesduring a stapling operation. When the distal tip of sled 382 is locatedbetween the location indicated by dotted lines 392 and 394, the stapleris in a “gripping” state (also “gripping stage”), in which first jaw 310and second jaw 360 close to a roughly parallel posture and can belightly gripping patient tissue. As the distal tip of sled 382 reachesthe location indicated by dotted line 394, the stapler transitions fromthe gripping state to a “clamping-not-yet-firing” state (also“clamping-not-yet-firing stage”), in which first jaw 310 and second jaw360 are held in close enough proximity so as to exert substantiveclamping force on the patient tissue. This clamping-not-yet-firing statecan provide some pre-stapling compression of the patient tissue, andhelp flatten the tissue to improve the chances of a successful staplingoperation.

As the distal tip of sled 382 reaches the location indicated by dottedline 396, the stapler has transitioned from the clamping-not-yet-firingstate to the “firing” state (also “firing stage”), in which sled 382pushes various ones of staple pushers 335 against corresponding staples330 and fires these staples 330 through staple slots 340. The staplingprocess ends when the distal tip of sled 382 has reached its goal at thelocation indicated by dotted line 398. This firing state may also betermed a “clamping” state that is separate from theclamping-not-yet-firing state.

According to some embodiments, the applied force or torque may bemonitored during the firing state, the clamping-not-yet-firing state,the gripping state, and/or a combination of any two or three of thesestates. In some examples, applied force or torque may be monitored andprocesses performed, such as those discussed in this disclosure, in thefiring state. In some examples, applied force or torque may be monitoredand processes performed, such as those discussed in this disclosure, inthe firing state and all or part of the clamping-not-yet-firing state.In some examples, different force or torque limit thresholds and/or useother parameters may be used for the firing and clamping-not-yet-firingstates.

According to some embodiments, feedback may be provided to a surgeonand/or other medical personnel during the stapling operation. In someexamples, a control unit in a computer-assisted system (e.g.,computer-assisted system 100) may estimate the likelihood of asuccessful stapling process in the clamping-not-yet-firing state andprovide such estimate to users through any appropriate method, includingthrough visual displays, auditory feedback, and/or the like. In someexamples, this feedback may be provided while the stapling process canbe readily reversed, so that no staples are expended and can be usedelsewhere during a procedure. In some embodiments, the computer-assistedsystem will inhibit the start of the firing state until the likelihoodof successful stapling is gauged to be sufficiently high.

In some embodiments, surgical instrument 200 and/or associatedcomputer-assisted system (e.g., computer-assisted system 100) isconfigured with user interfaces that make these three states distinctiveto the operator. For example, some embodiments provide differentcontrols for changing states through different combinations of knobs,buttons, switches, pedals, and other input devices. In some examples,for a teleoperational computer-assisted system, this computer-assistedsystem may be configured to do the following: (1) command entry into thegripping state, such as by commanding sled 382 move to a locationcorresponding to dotted line 392 at a gripping velocity, in response tosensing a pinching input on a master manipulator input device associatedwith an active stapler instrument, (2) command entry into theclamping-not-yet-firing state, such as by commanding sled 382 move to alocation corresponding to dotted line 394 at a clamping-not-yet-firingvelocity, in response to a depression of a first pedal, (3) commandentry into the firing state and continuation into the firing state, suchas by commanding sled 382 move to a location past dotted line 396, todotted line 398 at the distal end of end effector 220, at a firingvelocity. Some embodiments may also be configured with timeouts, suchthat the pinching motion, depression of the first pedal, and/ordepression of the second pedal result in commands for the associatedstates after associated predetermined periods of time have passed withthe pinching motion, first pedal depression, and/or second pedaldepression. In some embodiments, surgical instrument 200 or associatedcomputer-assisted system (e.g., computer-assisted system 100) isconfigured with user interfaces that combines from the user controlperspective the “gripping” and “clamping-not-yet-firing” states, or the“camping-not-yet-firing” and “firing” states. In some embodiments, asingle switch or pedal is provided for the operator to instruct entryinto the gripping state and transition to the clamping-not-yet-firingstate. In some embodiments, a single switch or pedal is provided for theoperator to instruct entry into the clamping-not-yet-firing state andtransition to the firing state.

FIG. 4 is a simplified diagram of a state machine 400 for operating anend effector according to some embodiments. One or more of the states410-490 of state machine 400 may be implemented, at least in part, inthe form of executable code stored on non-transient, tangible, machinereadable media that when run by one or more processors (e.g., theprocessor 150 in control unit 140) may cause the one or more processorsto implement one or more of the states 410-490. In some embodiments,state machine 400 may be implemented by an application, such as controlapplication 170. In some embodiments, state machine 400 may be used torestrict and/or limit the velocity set point of an actuator, such as theactuator controlling movement of reciprocating element 380, based on thetorque being applied by the actuator. In some embodiments, while statemachine 400 is operating, the torque of the actuator is monitored. Insome embodiments, state transitions between states 410-490 may occurwhen the indicated state transitions occur or optionally may occur atperiodic intervals based on execution of a control loop implementingstate machine 400.

State machine 400 begins in a start state 410. Upon direction and/orcommand of an operator, such as a surgeon, via the activation of one ormore controls, inputs, and/or the like, operation of the end effectortransitions to a pre-clamp state 420. In pre-clamp state 420, a velocityset point of the actuator, such as the actuator propelling reciprocatingelement 380, is set to an initial velocity v₀. In some examples,velocity v₀ may optionally be consistent with a maximum allowed velocityfor the actuator. In some embodiments, operation of the end effectorremains in pre-clamp state 420 until the actuator has moved a minimumdistance or reached an initial position (e.g., the positioncorresponding to dotted line 394). In some examples, the minimumdistance may correspond to a position where initial grasping of tissueoccurs, such as slightly before and/or after the distal end of flange384 encounters transitional edge 370 and the gap between anvil 360 andjaw 310 begins to close. In some embodiments, this initial grasping oftissue is associated with the “gripping” state discussed in conjunctionwith FIG. 3A and/or a before-gripping state applicable just before thegripping state. In some embodiments, this initial grasping of tissue isassociated with part or all of the “gripping” and“clamping-not-yet-firing” states discussed in conjunction with FIG. 3A.When the torque of the actuator exceeds a maximum torque, τ_(max),before reaching the minimum distance, state machine 400 transitions to afail state 490. State machine 400 may indicate the fail state 490 tohuman operators visually, aurally, or via some other feedback method.When the torque of the actuator does not exceed the maximum torque,state machine 400 transitions to an initial clamp state 430.

In the initial clamp state 430, the velocity set point of the actuatoris set to an initial clamp velocity v₁. Control of the actuator thencontinues at velocity v₁ until either a goal position is reached, suchas when reciprocating element 380 has been propelled to the distal endof end effector 220 or a torque threshold τ₁ is reached. Torque τ₁ islower than the maximum torque τ_(max). In some examples, velocity v₁ mayoptionally be the same velocity as the initial velocity v₀. Statemachine 400 may indicate the success state 480 to human operatorsvisually, aurally, and/or via some other feedback method. When the goalposition is reached, state machine 400 transitions to a success state480. When the torque of the actuator exceeds torque τ₁ before the goalposition is reached, state machine 400 transitions to a first slow clampstate 440.

In the first slow clamp state 440, the velocity set point of theactuator is set to a velocity v₂ lower than velocity v₁. Control of theactuator then continues at velocity v₂. While in the first slow clampstate 440, the torque of the actuator is further monitored to seewhether it is increasing or decreasing. When the torque of the actuatordecreases to a torque τ₂, which is lower than torque τ₁ (such as 5-20%lower than τ₁ and/or 1-3 N-m RANGE below τ₁), state machine 400transitions back to initial clamp state 430, where the velocity setpoint of the actuator is increased back to velocity v₁. The amount towhich torque τ₂ is lower than torque τ₁ may be set to introducehysteresis in the velocity control of the actuator to avoid excessthrashing of the velocity set point for the actuator. When the torque ofthe actuator increases to torque τ₃, state machine 400 transitions to asecond slow clamp state 450. Torque τ₃ is lower than the maximum torqueτ_(max), but is typically higher than torque τ₁ so that increasingtorques continue to result in lower velocity set points for theactuator. When the goal position is reached, state machine 400transitions to success state 480.

In the second slow clamp state 450, the velocity set point of theactuator is set to a velocity v₃ lower than velocity v₂. Control of theactuator then continues at velocity v₃. While in the second slow clampstate 450, the torque of the actuator is further monitored to seewhether it is increasing or decreasing. When the torque of the actuatordecreases to a torque τ₄, which is lower than torque τ₃, state machine400 transitions back to the first slow clamp state 440, where thevelocity of the actuator is increased. The amount to which torque τ₄ islower than torque τ₃ may be set to introduce hysteresis in the velocitycontrol of the actuator to avoid excess thrashing of the velocity setpoint for the actuator. When the torque of the actuator increases totorque τ₅, state machine 400 transitions to a wait state 460. Torque τ₅may optionally be the same or lower than the maximum torque τ_(max), butis typically higher than torque τ₃ so that increasing torques continueto result in lower velocity set points for the actuator. When the goalposition is reached, state machine 400 transitions to success state 480.

In wait state 460, state machine 400 pauses the operation for apredetermined period of time (also called a “pause period”). To pausethe operation in wait state 460, state machine 400 may pause theactuator by setting the velocity set point of the actuator to zero tocease movement of the actuator. In some examples, setting the velocityset point of the actuator to zero allows for additional time in whichthe grasped tissue may further desiccate. In some examples, statemachine 400 remains in wait state for a predetermined period of time, toprovide a temporal pause from stapler actuation. In some examples, thepredetermined period of time may optionally be implemented using ahardware and/or software timer. After the predetermined period of timetimes out, state machine 400 automatically transitions to a try state470.

In the try state 470, an attempt to move the actuator is made. Each timea try is attempted, a try counter is increased. In some examples, theattempt may optionally include setting the velocity set point of theactuator back to velocity v₃ or another velocity value. When movement ofthe actuator is possible and the torque of the actuator remains below atorque τ₆, which is lower than torque τ₅, the try counter is reset tozero and state machine 400 transitions back to the second slow clampstate 450, where the velocity set point of the actuator is increasedback to velocity v₃. The amount to which torque τ₆ is lower than torqueτ₅ may be set to introduce hysteresis in the velocity control of theactuator to avoid excess thrashing of the velocity set point for theactuator. When the torque of the actuator remains above torque τ₆,during try state 460, state machine 400 returns to wait state 460 towait an additional amount of time. State machine 400 may be configuredsuch that it can transition to wait state 460 only after a try period oftime has passed, a minimum try distance has been achieved, and/or both.When the try counter exceeds a maximum number of tries, state machine400 transitions to fail state 490.

In success state 480, successful stapling and cutting is detected andcontrol of the actuator is optionally reversed so that the jaws of theend effector open with a corresponding release of the grasped tissue. Inthe examples, of FIGS. 3A-3D, reversing the actuator includes pullingreciprocating element 380 in the proximal direction so that sled 382 ispulled out of jaw 310 and staple cartridge 320, flange 384 is pulled outof anvil 360 allowing anvil 360 to pivot open, and cutting blade 386 ispulled back into a safety position, such as a garaged position. In someexamples, success of the stapling and cutting operation may optionallybe reported to the operator using an audio and/or visual alert.

In fail state 490, failure to complete the stapling and cuttingoperation is detected because the actuator was not able to reach thegoal position. In the examples of FIGS. 3A-3D, this occurs whenreciprocating element 380 is not able to be propelled to the distal endof jaw 310 and anvil 360. While in fail state 490, an audio and/orvisual alert is reported to the operator indicating failure of thestapling and cutting operation. In some examples, reversing of theactuator may optionally be attempted, either automatically by the statemachine or at the express command of the operator.

As discussed above and further emphasized here, FIG. 4 is merely anexample which should not unduly limit the scope of the claims. One ofordinary skill in the art would recognize many variations, alternatives,and modifications. In some embodiments, properties of the end effectorand the actuator other than torque may alternatively be monitored andresult in the state transitions described above. In some examples, forceapplied by the actuator may be monitored instead of torque. In someembodiments, initial clamp state 430 and pre-clamp state 420 mayoptionally be combined into a single state. In some embodiments, thesecond slow clamp state 450 may be removed, such that state machine 400transitions from the first slow clamp state 400 to wait state 460 whenthe torque of the actuator is higher than torque τ₃. In someembodiments, the first slow clamp state 440 and the second slow clampstate 450 are removed, such that the process transitions from initialclamp state 430 to wait state 460 when the torque of the actuator ishigher than torque τ₁. In some embodiments, additional slow clamp statesmay optionally be added between the second slow clamp state 450 and waitstate 460 depending upon how many steps are desired in thevelocity-torque profile for the end effector.

In some embodiments, one or more techniques may optionally be used toreduce the effects of temporary transients in the application of thetorque thresholds. In some examples, the state transitions of statemachine 400 occur when the applied torque remains above or below thecorresponding torque threshold for a predetermined period of time. Insome examples, the predetermined period of time may optionally bedifferent for torque thresholds that decrease the velocity set point andtorque thresholds that increase the velocity set point. In someexamples, the state transitions of state machine 400 occur when anaverage value of the applied torque is above or below the correspondingtorque threshold. In some examples, the average is computed usingexponential smoothing. In some examples, the applied torque is low-passfiltered.

FIG. 5 is a simplified diagram of a velocity-torque profile 500 for theend effector of FIG. 3 according to some embodiments. As shown in FIG.5, velocity-torque profile 500 includes multiple velocity settings thatvary based on a monitored torque. In some examples, velocity-torqueprofile 500 is consistent with the velocity set points implemented bystate machine 400. In velocity-torque profile 500, the velocity setpoint of an actuator, such as the actuator for end effector 220, is setto velocity v₁ until the torque applied by the actuator exceeds torqueτ₁. Once torque τ₁ is exceeded, the velocity set point is reduced tovelocity v₂. The velocity of the actuator is then controlled at velocityv₂ until the torque applied by the actuator exceeds torque τ₃. Oncetorque τ₃ is exceeded, the velocity set point is reduced to velocity v₃.The velocity of the actuator is then controlled at velocity v₃ until thetorque applied by the actuator exceeds torque τ₅. Once torque τ₅ isexceeded, the velocity set point is reduced to zero. Velocity-torqueprofile 500 is further implemented using hysteresis such that thevelocity set point of the actuator is not increased back to velocitiesv₃, v₂, and v₁ until the torque of the actuator drops below torques τ₆,τ₄, and τ₂, respectively. Where torques τ₆, τ₄, and τ₂, are set belowtorques τ₅, τ₃, and τ₁, respectively

As discussed above and further emphasized here, FIG. 5 is merely anexample which should not unduly limit the scope of the claims. One ofordinary skill in the art would recognize many variations, alternatives,and modifications. In some embodiments, properties of the end effectorand the actuator other than torque may be used in the velocity profile.In some examples, force applied by the actuator may be used instead oftorque. In some embodiments, fewer and/or more than three steps mayoptionally be used in the velocity-torque profile. In some embodiments,velocity-torque profile 500 may optionally be implemented withouthysteresis by setting τ₂ equal to τ₁, setting τ₄ equal to τ₃, andsetting τ₆ equal to τ₅. In some embodiments, a smooth velocity-torqueprofile, with or without hysteresis, may optionally be used instead ofthe step profile of FIG. 5. In some examples, the velocity-torqueprofile may optionally be linear, include a series of s-shaped smoothsteps, and/or other monotonic profile where the velocity set point iscomputed as a function of the torque. In some embodiments, the torquesused to determine the velocity set point may optionally be averagetorques, low-pass filtered torques, and/or the like.

FIG. 6 is a simplified diagram of a method 600 for performing a staplingand cutting operation according to some embodiments. One or more of theprocesses 605-650 of method 600 may be implemented, at least in part, inthe form of executable code stored on non-transient, tangible, machinereadable media. This executable code, when run by one or more processors(e.g., the processor 150 in control unit 140), may cause the one or moreprocessors to perform one or more of the processes 605-650. In someembodiments, method 600 may be performed by an application, such ascontrol application 170. In some embodiments, method 600 may be used tolimit the velocity of an actuator used to actuate a reciprocatingelement, such as reciprocating element 380, based on a torque beingapplied by the actuator. In some embodiments, the stapling and cuttingoperation of method 600 may be performed according to state machine 400and/or velocity-torque profile 500. In some embodiments, the tests ofprocesses 615, 620, and 630 may occur concurrently and/or in any order.

At a process 605, an end effector is actuated (also “fired”). The endeffector, such as end effector 220, is fired by causing an actuator,such as an actuator in drive system 240, to apply a torque that is usedto control at least one DOF of the end effector. In some examples, theactuator is controlled by sending one or more signals, such as acurrent, a voltage, a pulse-width modulated signal, and/or the like tothe actuator. The actual effects of the firing of the end effectordepend on the design, use, and purpose of the end effector. In someexamples, firing of the end effector begins by setting a velocity setpoint of the actuator, such as the setting of the velocity set point tovelocity v₀ during pre-clamp state 420. Using the examples, of FIGS. 2and 3A-3D, the actuator applies a force to drive mechanism 250 whichcauses reciprocating element 380 to be moved toward the distal end ofend effector 220. This in turn causes a reduction in the gap betweenanvil 360 and jaw 310 so that tissue is grasped, staples 330 are forcedthrough the grasped tissue by sled 382 acting on staple pushers 335, andcutting blade 386 cuts the grasped tissue. The firing of the endeffector continues until success or failure of the firing is determinedand/or it is interrupted by an operator.

At a process 610, the applied torque is monitored. Using one or moresensors and/or control algorithms the torque being applied by theactuator is monitored as the end effector is fired. For example, whenthe actuator is a motor, current applied to the motor may be monitoredand used to determine a torque being applied by the motor.

At a process 615, it is determined whether the end effector is at a goalposition. Using one or more sensors, a position of the actuator and/or aposition of a detectable location on the end effector is monitored. Insome examples, the sensors may measure a rotation angle of a drive shaftof the actuator. In some examples, the one or more sensors may include ashaft encoder, Hall Effect sensor, and/or the like. In the examples, ofFIGS. 3A-3D, the goal position corresponds to movement of reciprocatingelement 380 to the distal end of end effector 220 so that all of thestaples 330 have been fired through the grasped tissue and cutting blade386 has cut through the grasped tissue. When the goal position isreached, the operation of the end effector is considered successful andthe velocity set point is set to zero. In some examples, an operator ofthe system is also notified via an audio and/or visual alert. In someexamples, success is consistent with success state 480. When the goalposition is not yet reached, the monitored torque is compared againstone or more torque thresholds beginning with a process 620.

At the process 620, it is determined whether the applied torque is abovea first torque threshold. The applied torque monitored during process610 is compared to the first torque threshold to determine whether theactuator is applying more torque to the end effector than is desired. Insome examples, the first torque threshold optionally varies dependingupon the current velocity set point. In the examples, of FIGS. 4 and 5,the first torque threshold corresponds to one or more of the torques τ₁,τ₃, and/or τ₅. When the applied torque is above the first torquethreshold, the velocity set point is reduced using a process 625. Whenthe applied torque is not above the first threshold, the torque iscompared to a second torque threshold using a process 630.

At the process 625, the velocity set point is reduced. When the appliedtorque is above the first threshold, the velocity set point of theactuator is reduced to allow additional time for the grasped tissue tofurther desiccate, slow down the firing of one or more staples, and/orthe like. In some examples, the velocity set point may be reduced afixed amount, a percentage amount, according to a velocity-torqueprofile, and/or the like. In the examples of FIGS. 4 and 5, the velocityset point is reduced to v₂, v₃, or zero depending upon the previousvelocity set point and/or the first torque threshold used during process620. In some examples, the decreasing of the velocity set point isconsistent with the state transitions from initial clamp state 430 tothe first slow clamp state 440, from the first slow clamp state 440 tosecond slow clamp state 450, and/or from the second slow clamp state 450to wait state 460. After the velocity set point is reduced, it is testedto determine whether it is reduced to zero using a process 640.

At the process 630, it is determined whether the applied torque is belowa second threshold. The applied torque monitored during process 610 iscompared to the second torque threshold to determine whether theactuator may be sped up. In some examples, the second torque thresholdis set lower than the first torque threshold in order to providehysteresis in the velocity set point. In some examples, the secondtorque threshold optionally varies depending upon the current velocityset point. In the examples, of FIGS. 4 and 5, the second torquethreshold corresponds to one or more of the torques τ₂, τ₄, and/or τ₆.When the applied torque is below the second torque threshold, thevelocity set point is increased using a process 635. When the appliedtorque is not below the second threshold, the torque is monitored againusing process 610.

At the process 635, the velocity set point is increased. When theapplied torque is below the second threshold, the velocity set point ofthe actuator is increased to allow faster operation of the end effector.In some examples, the velocity set point may be increased a fixed amount(e.g., 0.1 to 2 mm/sec), a percentage amount (e.g., 5-25 percent),according to a velocity-torque profile, and/or the like. In someexamples, when the velocity is at a maximum set point, the velocity setpoint is not further increased during process 635. In the examples ofFIGS. 4 and 5, the velocity set point is increased to v₁, v₂, or v₃depending upon the previous velocity set point and/or the second torquethreshold used during process 630. In some examples, the increasing ofthe velocity set point is consistent with the state transitions from trystate 470 to second slow clamp state 450, from second slow clamp state450 to the first slow clamp state 440, and/or from the first slow clampstate 440 to initial clamp state 430. After the velocity set point isincreased, the torque is monitored again using process 610.

At the process 640, it is determined whether the velocity set point iszero. When the velocity set point reaches zero, a delay is introducedusing a process 645. When the velocity set point is not yet at zero, thetorque is monitored again using process 610.

At the process 645, a wait (also “pause”) occurs. When the velocity setpoint reaches zero, firing of the end effector is delayed for apredetermined period of time (e.g., 1-10 sec). In some examples, thepredetermined period of time is tracked using a hardware and/or softwaretimer. In the examples of FIG. 4, process 645 corresponds to wait state460. After the delay times out, operation of the end effector is testedusing a process 650.

At the process 650, it is determined whether operation of the endeffector can continue. The velocity set point is set to a non-zerovalue, such as the velocity set point value before the last time process625 was performed, and the torque applied by the actuator is monitored.In the examples, of FIG. 4, process 650 corresponds to try state 470.When the torque applied by the actuator continues to be above a maximumtorque threshold, such as the first torque threshold used the last timeprocess 620 was performed, the firing of the end effector is consideredfailed and the velocity set point is set to zero. In some examples, thefiring of the end effector may optionally be reversed and/or one or moreaudio and/or visual alerts are optionally provided to an operator. Whenmovement at the non-zero velocity set point occurs without an excessiveapplied torque being detected, the velocity set point is retained andthe monitoring of the torque continues with process 610.

As discussed above and further emphasized here, FIG. 6 is merely anexample which should not unduly limit the scope of the claims. One ofordinary skill in the art would recognize many variations, alternatives,and modifications. In some embodiments, properties of the end effectorand the actuator other than torque may be monitored during process 610and tested during processes 620 and 630. In some embodiments, the waitor process 645 and/or the test of process 650 may be repeated one, two,or more times before failure is concluded. In this way, the method 600may pause the actuator multiple times and indicate a failure after apredetermined number of actuator pauses have occurred. In some examples,the number of repetitions may be tracked using a hardware or softwarecounter.

In some embodiments, one or more techniques may optionally be used toreduce the effects of temporary transients in the application of thetorque thresholds. In some examples, the comparisons of the appliedtorque to the first and second torque thresholds in processes 620 and630, respectively, determine whether the applied torque remains above orbelow the first and second torque thresholds for a predetermined periodof time. In some examples, the predetermined period of time mayoptionally be different for the first and second torque thresholds. Insome examples, the monitoring of the applied torque in process 610includes averaging the applied torque. In some examples, the averagingincludes using exponential smoothing. In some examples, the monitoringof the applied torque in process 610 includes low-pass filtering theapplied torque.

Some examples of control units, such as control unit 140 may includenon-transient, tangible, machine readable media that include executablecode that when run by one or more processors (e.g., processor 150) maycause the one or more processors to implement the states of statemachine 400, implement the velocity-torque profile 500, and/or performthe processes of method 600. Some common forms of machine readable mediathat may include the implementation of state machine 400, theimplementation of velocity-torque profile 500, and/or the processes ofmethod 600 are, for example, floppy disk, flexible disk, hard disk,magnetic tape, any other magnetic medium, CD-ROM, any other opticalmedium, punch cards, paper tape, any other physical medium with patternsof holes, RAM, PROM, EPROM, FLASH-EPROM, any other memory chip orcartridge, and/or any other medium from which a processor or computer isadapted to read.

Although illustrative embodiments have been shown and described, a widerange of modification, change and substitution is contemplated in theforegoing disclosure and in some instances, some features of theembodiments may be employed without a corresponding use of otherfeatures. One of ordinary skill in the art would recognize manyvariations, alternatives, and modifications. Thus, the scope of theinvention should be limited only by the following claims, and it isappropriate that the claims be construed broadly and in a mannerconsistent with the scope of the embodiments disclosed herein.

1. An instrument for use with a computer-assisted device, the instrumentcomprising: an end effector located at a distal end of the instrument;an actuator; and one or more drive mechanisms for coupling force ortorque from the actuator to the end effector; wherein to perform anoperation with the instrument, the computer-assisted device isconfigured to: set a velocity set point of the actuator to an initialvelocity; monitor force or torque applied by the actuator; when theapplied force or torque is above a first threshold, reduce the velocityset point; when the applied force or torque is below a second threshold,increase the velocity set point; when the applied force or torque isabove a maximum threshold, decrease the velocity set point to zero; anddrive the actuator based on the velocity set point; wherein the firstand second thresholds are lower than the maximum threshold.
 2. Theinstrument of claim 1, wherein the operation comprises one or more ofgrasping, stapling, and cutting. 3-4. (canceled)
 5. The instrument ofclaim 1, wherein the velocity set point is reduced and increasedaccording to a velocity profile.
 6. (canceled)
 7. The instrument ofclaim 1, wherein the velocity set point is reduced and increased tovelocity values computed based on the applied force or torque.
 8. Theinstrument of claim 1, wherein the first and second thresholds varybased on the applied force or torque.
 9. The instrument of claim 1,wherein when the applied force or torque is above the maximum threshold,the computer-assisted device is further configured to wait for apredetermined period of time before continuing the operation.
 10. Theinstrument of claim 9, wherein after the wait, the computer-assisteddevice is further configured to: set the velocity set point to anon-zero value; determine whether the applied force or torque continuesto be above the maximum threshold; and indicate a failure when theapplied force or torque continues to be above the maximum threshold. 11.(canceled)
 12. The instrument of claim 1, wherein the computer-assisteddevice is further configured to indicate a success when a goal positionis reached.
 13. The instrument of claim 1, wherein the velocity setpoint is reduced when the applied force or torque remains above thefirst threshold for a predetermined period of time.
 14. (canceled) 15.The instrument of claim 1, wherein to monitor the applied force ortorque the computer-assisted device is further configured to average theapplied force or torque. 16-26. (canceled)
 27. A method of operating ainstrument for use with a computer-assisted device, the methodcomprising: setting, by one or more processors, a velocity set point ofan actuator to an initial velocity; measuring, by the one or moreprocessors, a force or torque applied by the actuator; when the appliedforce or torque is above a first threshold, reducing, by the one or moreprocessors, the velocity set point; when the applied force or torque isbelow a second threshold, increasing, by the one or more processors, thevelocity set point; when the applied force or torque is above a maximumthreshold, decreasing, by the one or more processors, the velocity setpoint to zero; and driving, by the one or more processors, one or moredegrees of freedom of an end effector of the instrument using theactuator; wherein the first and second thresholds are lower than themaximum threshold.
 28. The method of claim 27, further comprising usingthe actuator to perform one or more of grasping, stapling, and cutting.29-30. (canceled)
 31. The method of claim 27, wherein the velocity setpoint is reduced and increased according to a velocity profile. 32.(canceled)
 33. The method of claim 27, wherein the velocity set point isreduced and increased to velocity values computed based on the appliedforce or torque.
 34. (canceled)
 35. The method of claim 27, furthercomprising indicating a success when a goal position is reached.
 36. Anon-transitory machine-readable medium comprising a plurality ofmachine-readable instructions which when executed by one or moreprocessors associated with a computer-assisted device are adapted tocause the one or more processors to perform a method comprising: settinga velocity set point of an actuator to an initial velocity; measuring aforce or torque applied by the actuator; when the applied force ortorque is above a first threshold, reducing the velocity set point; whenthe applied force or torque is below a second threshold, increasing thevelocity set point; when the applied force or torque is above a maximumthreshold, decreasing the velocity set point to zero; and driving one ormore degrees of freedom of an end effector of a instrument using theactuator; wherein the first and second thresholds are lower than themaximum threshold.
 37. The non-transitory machine-readable medium ofclaim 36, wherein the method further comprises using the actuator toperform one or more of grasping, stapling, and cutting. 38-39.(canceled)
 40. The non-transitory machine-readable medium of claim 36,wherein the velocity set point is reduced and increased according to avelocity profile.
 41. (canceled)
 42. The non-transitory machine-readablemedium of claim 36, wherein the velocity set point is reduced andincreased to velocity values computed based on the applied force ortorque.
 43. (canceled)
 44. The non-transitory machine-readable medium ofclaim 36, wherein the method further comprises indicating a success whena goal position is reached.